RADIATION!


Another way of transfering thermal energy is radiation.
Radiation is the emission of infrared waves from the surface of all bodies,transmitted without the aid of a medium. These infra red waves travel through straight lines.
Radiation, unlike convection and conduction can take place through a vacuum. Eg. The sun emitting thermal energy to te Earth uses radiation. It emits its energy through electromagnetic waves . Heat readiation is able to travel all directions!

A good emitter of radiant heat is also a good absorber.
A poor emmiter of radiant heat is also a poor absorber.


Factors affecting infrared radiation:D
Colour and texture
-black surfaces are better absorbers and better emmiters of infrared radiation
-shiny and white surfaces are poorer absorbers.
-rough surfaces are better for heat transfer


Surface temperature
-higher the temperature of the surface of the object relative to the surrounding temperature,the higher rate of infrared radiation.

Surface area
objects with a larger surface area will emit infrared radiation at a higher rate


Applications of radiation[:

Vacuum flask is designed to keep liquids hot through conduction,convection,evaporation and radiation. Conduction and convention through are prevented by the vacuum between the double-glass walls of the flask. Conduction through the trapped air is minimal since air is a poor conductor of heat. The stopper is made of plastic which is a poor conductor of heat. The walls of the glass are silvered so as to reflect radiant heat back into the hot liquid.

TAKEN FROM:http://www.blurtit.com/q965156.html

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